Not sure if that's the most optimized way to create custom coloured Ext buttons, but what happen is that the number of selectors hit the limit and triggered the bug. I may not need all the coloured buttons nor all the components styling but i am seeing this as a potential problem in the future as i am still early in the development phase for a hugely customized theme.

Currently, I am manually splitting the files in twos. But was wondering if there are other solutions.

However, I'm concerned about whether or not the application will still be able to find the stylesheets once they've been split. If anyone who understands this stuff better than I do could take a look at this and let me know whether this script would work with ExtJS 4.2, I'd appreciate it.

If you use Sencha Cmd to build your application, the production optimized CSS file will not contain rules for components that you don't use in your application. This reduces the number of rules in your CSS file.

For example, if you don't use the Slider component, you will not see any slider specific CSS rules.